The invention relates to a reforming reactor having a reaction space which is filled with a catalyst material in the form of pellets (sometimes referred to herein as a "catalyst pellet fill") and has a movable wall which exerts pressure on the catalyst pellets to hold them in position.
Numerous types of reforming reactors with a catalyst pellet fill charged in the reaction chamber are known, and are used, for example, for producing hydrogen as fuel for a fuel cell arrangement. Reforming reactors of this type are disclosed, for example, in German patent documents DE 44 23 587 A1 and DE 44 20 752 A1.
Particularly, in the case of mobile applications, for example, when used in fuel-cell-operated motor vehicles, jolts occur which, in the case of a catalyst pellet fill which is freely movable within the reaction chamber, may result in increased abrasion of the pellets. Such abrasion is undesirable because it may cause clogging or otherwise impair the components which are connected downstream. In addition, in the case of a loose pellet fill, vehicle position changes result in corresponding position changes of the catalyst material within the reforming reactor. In extreme situations, for example, in the case of steep slopes, this may have a disadvantageous effect on the uniform gas distribution and thus on the efficiency of the reactor.
In the reforming reactor referred to above, these difficulties are resolved by providing a movable reaction space wall which, on the one hand, permits the gas to pass through and, on the other hand, exerts position-fixing pressure onto the catalyst pellet fill. A reactor of this construction is disclosed in the Japanese Published Patent Application JP 63-21202 (A). There, the catalyst pellet fill charged into a tube-shaped reaction chamber is situated on a porous carrier plate and is covered on the top side by a reaction chamber cover. The latter is also porous, is arranged in a movable manner, and is pressed onto the catalyst pellet fill by means of coil springs which are supported on a reactor housing wall. The covering cap is arranged in a movable manner in order to permit an exchange of the catalyst material when the cap is removed.
Such an exchange or a refilling of catalyst material may be necessary from time to time, especially in the case of reforming reactors for producing hydrogen in mobile applications. Particularly in applications in vehicles, a compact arrangement of the gas production components is desirable for installation of the reforming reactor (for example, for producing hydrogen for a fuel cell system). Because of the limited narrow space conditions in the vehicle, it is undesirable to have to remove the reaction chamber covering of the reactor as a whole in order refill catalyst material. There is also the danger that, in case of complete removal of the covering, the catalyst material will come in contact with ambient oxygen over a large surface, which frequently damages the active catalyst material.
One object of the invention, therefore, is to provide a reforming reactor of the initially mentioned type which is particularly suitable for mobile applications (for example, for producing hydrogen for a fuel cell system of a motor vehicle).
Another object of the invention is to provide such a reforming reactor which permits a comparatively simple and trouble free refilling of catalyst material into the reaction chamber.
These and other objects and advantages are achieved by the reforming reactor according to the invention, in which the reaction space can be filled from the outside through a passage opening formed in the reaction space walls. In this reforming reactor, on the one hand, the catalyst pellet fill is subjected to a position-fixing pressure which largely prevents abrasion of the catalyst pellets of a loose pellet fill due to the swirling, particularly as the result of vehicle jolts, when used in motor vehicles. The development of fine abrasion dust which may cause clogging within the catalyst pellet fill, or of a filter connected downstream, is thus largely prevented. This, in turn prevents an increased pressure drop (and therefore a deterioration of the reforming characteristics) over the reforming reactor as the result of such clogging.
On the other hand, because the reforming reactor has a charging device by which catalyst material can be charged from the outside through a passage opening in one of the reaction space walls, it is unnecessary to remove a whole reaction space wall in order to refill or exchange catalyst material. Thus, there is no danger that the active catalyst material situated in the reaction space will come in contact with the outside atmosphere (for example, with damaging ambient oxygen) on the whole surface situated opposite the concerned reaction space wall. On the contrary, such contact is limited to the surface of the passage opening of the charging device, which can clearly be kept smaller than that of a whole reaction space wall.
According to the invention, the charging device contains a charging tube, one end of which leads into the passage opening of the pertaining reaction space wall, and the other end of which can receive catalyst material from the outside. The charging tube can be securely closed off against the passing-through of catalyst material by means of a closing plunger, which may, depending on the application, be gas-permeable.
In another embodiment of the invention, the charging device has a movable reaction space wall which can be moved back against the direction of the applied pressure during a refilling operation. This makes it possible to relieve the catalyst pellet fill from the position-fixing applied pressure, and to create space for replenishing catalyst material. In this manner, catalyst can be pushed into the reaction space without a high compressive load, which minimizes resulting abrasion of the catalyst pellets.
In still another embodiment of the invention, the passage opening for charging catalyst material into reaction space is provided in the movable reaction space wall, which is also perforated so that it is gas-permeable. The catalyst material is replenished by way of a charging tube, one end of which is fixed to the movable reaction space wall, so that it can simultaneously be used as an operating element for moving this reaction space wall back against the applied pressure. The tube extends through a gas inlet or gas outlet space which adjoins the movable reaction space wall on the side opposite the reaction space, and leads into a filling neck which can be covered toward the outside by a detachable closing device. Depending on the application, in this case the charging tube can be disposed in a gas-tight manner in the filling neck. Alternatively, in an implementation which is not gas tight, gas can flow from the gas inlet space into the filling neck, and from there through the charging tube and the (gas-permeable) closing plunger, into the reaction space. The latter arrangement has the advantage that the catalyst material situated in the area of the charging tube will also be able to actively participate in the reforming reaction.
Yet another embodiment of the reforming reactor according to the invention has an outlet device arranged in the lower portion of the reaction chamber, by means of which catalyst material can be discharged from the reaction space. Thus, it is also unnecessary to completely remove a reaction space wall or the reaction space covering for partial or complete removal of catalyst material from the reaction space.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.